I needed a workbench for working on stained glass (so no heavy pushing like with hand planing). I took a spare sheet of 3/4" particleboard with melamine finish on the faces and cut it to 6x3', rounded the corners with a jigsaw and attached 4 IKEA screw on legs that I had from an old table. The legs are very strong but the table seems to be a bit too long for the material and if I press in the middle it bends considerably and springs back to place with a wobble when Iet go. This wouldn't be a problem except that for stained glass I need to do very precise movements and I can't have the thing wobbling on me every time I make a cut.

I thought about installing edging with some scrap pine that I have except that I rounded over the edges and it's going to look ridiculous.

I also thought about adding another set of IKEA legs in the middle but they don't make them anymore.

The last thing I thought about is screwing two strips of pine running parallel to each other, fastened to the underside of the table so that you wouldn't see them but I'm not sure if that would work (though it's the same effect as siding, right?)

I think the search term you're looking for is table apron. If you provided more detail about the legs, I'm sure we could offer suggestions on integration.
– Aloysius DefenestrateJan 29 '17 at 19:11

If you have a long table and the 4 legs are currently at the corners, try moving them inwards 1/4 length from each end. This reduces the length of the span between the legs and reduces sagging a lot.
– jpaJan 30 '17 at 11:57

2 Answers
2

Think of a classic dining table, which has a framework underneath (commonly called the apron) that supports the table top. I think this is what you should probably build on to the workbench. Failing that join each pair of legs, front and back, with long boards (used edge-up) that run under the long dimension of the table. If using construction wood 3x1s might be enough but use 4x1s or 3x2s if you want to err on the side of caution.

Regarding the material you used for the top, particleboard (UK: chipboard) is quite a good choice for worktops if used appropriately. Unfortunately long unsupported spans is not one of the things it does well, in fact in thinner sections it's notorious for bowing ....even under its own weight!